This invention relates to a locking mechanism, to a locking bolt (sometimes referred to as a locking pin), to an actuator for the lock mechanism and to a method of assembly. The locking mechanism comprises a first part (10) and a second part (12), the first part and second part being securable together by way of at least one locking member (26) carried by the first part. The locking member(s) is driven into its locking position by an actuator (24) which is in turn driven by a key-operated lock carried by the first part. The first part has a first end portion (16). The first part has a second end (32) opposed to its first end portion (16), and has a recess (18) in its second end (32) which is adapted to accommodate the key-operated lock and the actuator (24). The actuator has a cam section (42) whereby rotation of the actuator causes radial movement of the locking member(s) (26). The actuator has a first support plate (72) located between the cam section (42) and the key-operated lock and a second support plate (74) located to the opposed side of the cam section (42), the support plates (72, 74) being adapted for sliding engagement with the substantially circular internal surface of the recess (18). The first support plate (72) has an acircular periphery (76, 80) whereby the first support plate can pass the locking member(s) (26) during assembly of the first part, so that the actuator can be made as a one-piece construction. There is also provided a first part of a locking bolt, and a method of assembling the first part of a locking bolt.